LinkedIn Communication Architecture

Slide 1: LINKEDIN COMMUNICATION ARCHITECTURE Ruslan Belkin, Sean Dawson TS-5234

Slide 2: Learn how we at LinkedIn built and evolved scalable communication platform for the world’s largest professional network 2008 JavaOneSM Conference | java.sun.com/javaone | 2

Slide 3: Agenda Why are we doing this talk LinkedIn Communication Platform at a glance • Evolution of LinkedIn Communication System • Evolution of the Network Updates System Scaling the system: from 0 to 22M members Q&A 2008 JavaOneSM Conference | java.sun.com/javaone | 3

Slide 4: Why are we doing this talk? Share our experience in building the world-largest professional network in Java™ Describe the evolution of the communication platform Share lessons we learned so you could benefit from our successes, mistakes and experience 2008 JavaOneSM Conference | java.sun.com/javaone | 4

Slide 5: LinkedIn Communication Platform Quick Tour 2008 JavaOneSM Conference | java.sun.com/javaone | 5

Slide 8: LinkedIn Communication Platform The Numbers 22M members 130M connections 2M email messages per day 250K invitations per day 2008 JavaOneSM Conference | java.sun.com/javaone | 8

Slide 9: LinkedIn Communication Platform The Setup Sun™ x86 platform and Sparc production hardware running Solaris™ Operating System 100% Java programming language Tomcat and Jetty as application servers Oracle and MySQL as DBs ActiveMQ for JMS Lucene as a foundation for search Spring as a glue Mac for development 2008 JavaOneSM Conference | java.sun.com/javaone | 9

Slide 10: LinkedIn Communication Platform The Communication Service The network updates service • Permanent message storage • Short-lived notifications (events) • InBox messages • Distribution across various • Emails affiliations and groups • Batching, delayed delivery • Time decay • Bounce, cancellation • Events grouping and • Actionable content prioritization • Rich email content 2008 JavaOneSM Conference | java.sun.com/javaone | 10

Slide 11: The Communication Service How is it different: • Workflow oriented • Messages reference other objects in the system • Incorporates email delivery • Batching of messages • Message cancellation • Delayed delivery, customer service review queues, abuse controls • Supports reminders and bounce notifications to users Has undergone continuous improvements throughout life of LinkedIn 2008 JavaOneSM Conference | java.sun.com/javaone | 11

Slide 12: Message Creation 2008 JavaOneSM Conference | java.sun.com/javaone | 12

Slide 13: Message Delivery 2008 JavaOneSM Conference | java.sun.com/javaone | 13

Slide 14: The Communication Service Message Creation Message Delivery • Clients post messages via • Message delivery is triggered by asynchronous Java Communications clients or by scheduled processes API using JMS • Delivery actions are asynchronous • Messages then are routed via • Messages can be batched for routing service to the appropriate delivery into a single email message mailbox or directly for email • Message content is processed processing through the JavaServer Page™ (JSP™) • Multiple member or guest technology for pretty formatting databases are supported • The scheduler can take into account the time, delivery preferences, system load • Bounced messages are processed and redelivered if needed • Reminder system works the same way as message delivery system 2008 JavaOneSM Conference | java.sun.com/javaone | 14

Slide 15: The Communication Service SOA architecture Wireable components build around LinkedIn Spring extensions Spring HTTP-RPC Heavy use of JMS and asynchronous flows 2008 JavaOneSM Conference | java.sun.com/javaone | 15

Slide 16: The Communication Service Failure Recovery Possible failures: • Messages can bounce • Messages can get lost: • Database problems • Bugs in the code • Bugs in the content processing of emails • Various services may become unavailable Avoiding the downtime 2008 JavaOneSM Conference | java.sun.com/javaone | 16

Slide 17: The Communication Service How do we scale it? Functional partitioning: • sent, received, archived, etc. Class partitioning: • Member mailboxes, guest mailboxes, corporate mailboxes Range partitioning: • Member ID range • Email lexicographical range Asynchronous flows 2008 JavaOneSM Conference | java.sun.com/javaone | 17

Slide 18: Network Updates Service What is your network up to? The goal is to have a flexible service for distributing many types of short-lived updates Availability across a number of clients (web apps, RSS, API, LinkedIn Mobile, third-party…) 2008 JavaOneSM Conference | java.sun.com/javaone | 18

Slide 19: Network Updates Service Motivation Homepage circa 2007 Poor UI • Cluttered • Where does new content go? Poor Backend Integration • Many different service calls • Takes a long time to gather all of the data 2008 JavaOneSM Conference | java.sun.com/javaone | 19

Slide 20: Network Updates Service Motivation Homepage circa 2008 Clean UI • Eliminates contention for homepage real estate Clean Backend • Single call to fetch updates • Consistent update format 2008 JavaOneSM Conference | java.sun.com/javaone | 20

Slide 21: Network Updates Service Iteration 1 Move existing homepage logic into a remote service, refactor homepage to use the new service Advantages • No user impact while API is being finalized • Improve performance by fetching updates in parallel • Reduce complexity of the web app • Updates become easily accessible to other clients 2008 JavaOneSM Conference | java.sun.com/javaone | 21

Slide 22: Network Updates Service Iteration 1 - API 2008 JavaOneSM Conference | java.sun.com/javaone | 22

Slide 23: Network Updates Service Iteration 1 - API Pull-based architecture Collectors • Responsible for gathering data • Parallel collection to improve performance Resolvers • Fetch state, batch lookup queries, etc… • Use EHCache to cache global data (e.g., member info) Rendering • Transform each object into its XML representation 2008 JavaOneSM Conference | java.sun.com/javaone | 23

Slide 24: Network Updates Service Iteration 1 - Example UpdateQueryCriteria query = UpdateQueryCriteria.createDefaultCriteria() .setMemberID(2) .setRequestedTypes(NetworkUpdateType.CONNECTION) .setCutoffDate(…) .setMaxNumberOfUpdates(10); MyNetworkUpdatesService service = getService(MyNetworkUpdatesService.class); DataTree update = service.getNetworkUpdatesSumary(query); 2008 JavaOneSM Conference | java.sun.com/javaone | 24

Slide 25: Network Updates Service Iteration 1 - Example <updates> <NCON> <connection> <id>2</id> <firstName>Chris</firstNa me> <lastName>Yee</lastName> </connection> </NCON> </updates> 2008 JavaOneSM Conference | java.sun.com/javaone | 25

Slide 26: Network Updates Service Iteration 1 Lessons learned: • Centralizing updates into a single service leaves a single point of failure • Be prepared to spend time tuning the HttpConnectionManager (timeouts, max connections) • While the system was stabilizing, it was affecting all users; should have rolled the new service out to a small subset! • Don’t use “Least Frequently Used” (LFU) in a large EHCache—very bad performance! 2008 JavaOneSM Conference | java.sun.com/javaone | 26

Slide 27: Network Updates Service Iteration 2 Hollywood Principle: “Don’t call me, I’ll call you” Push update when an event occurs Reading is much quicker since we don’t have to search for the data! Tradeoffs • Distributed updates may never be read • More storage space needed 2008 JavaOneSM Conference | java.sun.com/javaone | 27

Slide 28: Network Updates Service Iteration 2 - Pushing Events 2008 JavaOneSM Conference | java.sun.com/javaone | 28

Slide 29: Network Updates Service Iteration 2 - Reading Updates 2008 JavaOneSM Conference | java.sun.com/javaone | 29

Slide 30: Network Updates Service Iteration 2 Pushing Updates • Updates are delivered via JMS • Aggregate data stored in 1 CLOB column for each target user • Incoming updates are merged into the aggregate structure using optimistic locking to avoid lock contention Reading Updates • Add a new collector that reads from the Update Database • Use Digesters to perform arbitrary transformations on the stream of updates (e.g, collapse 10 updates from a user into 1) 2008 JavaOneSM Conference | java.sun.com/javaone | 30

Slide 31: Network Updates Service Iteration 2 Lessons learned: • Underestimated the volume of updates to be processed • CLOB block size was set to 8k, leading to a lot of wasted space (which isn’t reclaimed!) • Real-time monitoring/configuration with Java Management Extension (JMX™) specification was extremely helpful 2008 JavaOneSM Conference | java.sun.com/javaone | 31

Slide 32: Network Updates Service Iteration 3 Updating a CLOB is expensive Goal: Minimize the number of CLOB updates • Use an overflow buffer • Reduce the size of the updates 2008 JavaOneSM Conference | java.sun.com/javaone | 32

Slide 33: Network Updates Service Iteration 3 - Overflow Buffer Add VARCHAR(4000) column that acts as a buffer When the buffer is full, dump it to the CLOB and reset Avoids over 90% of CLOB updates (depending on type), while still retaining the flexibility for more storage 2008 JavaOneSM Conference | java.sun.com/javaone | 33

Slide 34: Scaling the system What you learn as you scale: What to do: • A single database does not work • Partition everything: • Referential integrity will not be • by user groups possible • by domain • Cost becomes a factor: • by function databases, hardware, licenses, • Caching is good even when it’s storage, power only modestly effective • Any data loss is a problem • Give up on 100% data integrity • Data warehousing and analytics • Build for asynchronous flows becomes a problem • Build with reporting in mind • Your system becomes a target • Expect your system to fail at any for spamming exploits, data point scraping, etc. • Never underestimate growth trajectory 2008 JavaOneSM Conference | java.sun.com/javaone | 34

Slide 35: LinkedIn Communication Architecture Build with scalability in mind - never know when your business will take off Expect to do a lot of architecture and code refactoring as you learn and appreciate growth challenges 2008 JavaOneSM Conference | java.sun.com/javaone | 35

Slide 36: LinkedIn Communication Architecture Ruslan Belkin (http://www.linkedin.com/in/rbelkin) Sean Dawson (http://www.linkedin.com/in/seandawson) We are hiring!

Slide 37: The Communication Service LinkedIn Spring Extensions Automatic context instantiation Support for Builder Pattern from multiple spring files Custom property editors: LinkedIn Spring Components • Timespan (30s, 4h34m, etc.) Property expansion • Memory Size, etc. Automatic termination handling 2008 JavaOneSM Conference | java.sun.com/javaone | 37

Slide 38: The Communication Service LinkedIn Spring Extensions Comm-server/ cmpt/ components/ ccsServiceExporter.spring comm.spring jmx.spring comm-server.properties corpMboxServiceExporter.spring main.spring comm-server.spring memberMboxServiceExporter.spring comm.properties guestMboxServiceExporter.spring build.xml impl/ … 2008 JavaOneSM Conference | java.sun.com/javaone | 38

Slide 39: The Communication Service LinkedIn Spring Extensions … <bean id="resolver” class="com.linkedin.comm.pub.impl.MessageAddressResolver"> <lin:config> <property name="resolverDB" ref="resolverDB"/> <property name="eos" ref="eos"/> <property name="els" ref="eos"/> <property name="memberAccessor" ref="coreMemberAccessor"/> </lin:config> </bean> … 2008 JavaOneSM Conference | java.sun.com/javaone | 39

Slide 40: The Communication Service LinkedIn Spring Extensions (Builder) private final MessageAddressResolverDB _resolverDB; … MessageAddressResolver(Config config) { … } … public static class Config { private MessageAddressResolverDB _resolverDB; public MessageAddressResolverDB getResolverDB() { return ConfigHelper.getRequired(_resolverDB); } public void setResolverDB(MessageAddressResolverDB resolverDB) { _resolverDB = resolverDB; } }/*Config*/ 2008 JavaOneSM Conference | java.sun.com/javaone | 40

Slide 41: The Communication Service LinkedIn Spring Extensions (Components) … <lin:component id="remoteContentCommunicationService" location="comm-server-client-cmpt"> <lin:wire property-name="activemq.producer.brokerURL" property- value="${activemq.producer.brokerURL}"/> <lin:wire property-name="comm.server.httpRpc.url" property- value="${leo.comm.server.httpRpc.url}"/> </lin:component> … 2008 JavaOneSM Conference | java.sun.com/javaone | 41

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